Re: Atari ROM port ISA

[Michael Schmitz <schmitzmic@googlemail.com>]

Geert,
> On Sat, Apr 21, 2012 at 10:20, Geert Uytterhoeven<geert@linux-m68k.org>  wrote:
>>> I've had a look at the NetUSBee docs and see that the USB part of it does
>>> require 8 bit writes but little endian 16 bit reads. So we will need to
>>> retain the 16 bit reads for potential USB support there.
>> OK. But you ain't gonna get the right 16 bits using
>>
>> #define rom_in_be16(addr) \
>>         ({ u16 __v = (*(__force volatile u16 *) (addr)); __v>>= 8; __v; })
>> #define rom_in_le16(addr) \
>>         ({ u16 __v = le16_to_cpu(*(__force volatile u16 *) (addr));
>> __v>>= 8; __v; })
>>
>> as they both do a 16-bit read and shift the result.
>> Perhaps it should just be a 32-bit read instead?
Correct - the 16 bit read should not do any shifts instead.
>> Are the schematics publicly available?
> I found netusbee.zip.
> Unfortunately I (my computer) can't grok the schematics files.
Same here - I'm sure software to read these is available somewhere. I 
did not look closely though.
> However, program_spec.txt says (a.o., I encourage all interested
> parties to read it in full):
DId that ...
> | USB Data Reads
> | ==============
> |
> | Data Reads from USB are done at base address 0xFA8000 (activating a read
> | cycle) as a 16bit word.  Data appears on D8-15 as most significant byte, and
> | D0-7 as least significant byte.  Notice how A15 has to be set to 1 to make it
> | a USB cycle.
>
> So inw() should just do a 16-bit big-endian read.
You're right - I got my big vs. little endian mixed up. The ISP1160 
driver is a little-endian beast but the byte swap has been done in 
hardware here if I read the paragraph right.
> | USB Data Writes
> | ===============
> |
> | Data reads at base address 0xFB8000 actually cause data to be written.  As
> | the write interface is only 8 bits wide, the 16bits of data must be passed
> | through this "8 bit window".  The Least Signifant Byte is transferred first
> | by left shifting data once and added to 0xFA8000.  This is followed by the
> | Most significant byte, transferred by left shifting data once and then added
> | to 0xFB8000.  On this last cycle is where the transfer is actually done.
> | Notice how A15 has to be set to 1 to make it a USB cycle.
>
> So outw() should do 2 byte reads.
Correct again  - the A15 we can implement via the address field itself 
(just as the USB command vs. data cycle on A14). The ISP1160 driver has 
provisions to use two 8-bit writes in place of a 16 bit one but it might 
be cleaner to implement the 16 bit write the way the USB driver needs it.

Now - does anyone here on this list or on debian-68k own such hardware 
and would be in a position to test a USB driver written to this spec? Is 
the hardware still for sale?
(Not that I am at all sure whether the ISP1160 driver will run in a 
timer polled mode at all ...)

Cheers,

   Michael